The European Commission is proposing that EU governments make direct money transfers to Iran's central bank to avoid US penalties, an EU official said, in what would be the most forthright challenge to Washington's newly reimposed sanctions.

The step, which would seek to bypass the US financial system, would allow European companies to repay Iran for oil exports and repatriate Iranian funds in Europe, a senior EU official said, although the details were still to be worked out.

The European Union, once Iran's biggest oil importer, is determined to save the nuclear accord, that US President Donald Trump abandoned on 8 May. "Commission President Jean-Claude Juncker has proposed this to member states. We now need to work out how we can facilitate oil payments and repatriate Iranian funds in the European Union to Iran's central bank," said the EU official, who is directly involved in the discussions.

The US Treasury announced on Tuesday more sanctions on officials of the Iranian central bank, including its governor, Valiollah Seif. But the EU official said the bloc believes that does not sanction the central bank itself.

The European energy commissioner, Miguel Arias Canete, will discuss the idea with Iranian officials in Tehran during his trip this weekend, the EU official said. Then it will be up to EU governments to take a final decision.